At the present time, tools, for example, wear resistant tools, sliding members and cutting tools, such as cold forging and hot forging tools, e.g., punches and headers, require wear resistance, sliding properties, and fracture resistance. These tools employ the technique to improve wear resistance, sliding properties, and fracture resistance by forming different coating layers onto a surface of a substrate made of a hard material, such as WC-based cemented carbide, TiCN-based cermet, ceramics, diamond, or cBN.
As the coating layer, a TiCN layer and a TiAlN layer are generally widely employed, whereas various improvements are made to enhance wear resistance and fracture resistance.
For example, patent document 1 describes a cutting tool in which a surface of a substrate is coated with a wear resistant coating containing at least one extremely high hardness ultrafine particulate compound selected from the group consisting of B4C, BN, TiB2, TiB, TiC, WC, SiC, SiNx (x=0.5 to 1.33), and Al2O3. The document discloses that the hardness of the coating is improved by containing the ultrafine particulate compound. Patent document 2 discloses a coating layer composed of elongated TiAlN crystals having an average value of 1.5 to 7 in the aspect ratio of the crystal width, and describes that the coating layer has excellent wear resistance and oxidation resistance. Patent document 3 discloses a tool with hard coatings having different compositions deposited on a surface of a substrate.